In recent years, as a window glass for a vehicle such as an automobile and a window glass for a building material to be attached to a building construction such as a house or a building, demands for a transparent resin plate are increasing instead of a conventional inorganic glass plate. Particularly, for a vehicle such as an automobile, for weight saving, use of a transparent resin plate as a window material has been proposed, and especially, an aromatic polycarbonate transparent resin plate is excellent in fracture resistance, transparency, light weight properties, easy processability, etc., and its use has been studied as a promising window material for a vehicle. However, such a transparent resin plate has had problems with respect to the abrasion resistance when it is used in place of a glass plate. Therefore, it has been proposed to form a coating film on the surface of a transparent resin plate by means of various hard coating agents, for the purpose of improving the abrasion resistance of the transparent resin plate.
For such a hard coating agent, in order to form a coating film having high hardness, a condensation reaction of silanol groups which can form siloxane bonds is employed as the curing system, and an organopolysiloxane-containing composition to obtain a coating film having a higher performance with respect to the abrasion resistance, and a process for producing a resin substrate having a hard coating layer by using it, have been proposed. However, the abrasion resistance of an obtainable resin substrate having a hard coating layer has not yet been reached a satisfactory level at present.
On the other hand, among organopolysiloxane-containing compositions, particularly with respect to a silicone rubber, a process for producing a silicone rubber protective film having hardness imparted to its surface while keeping its interior being flexible by utilizing ultraviolet curing, has been proposed (Patent Document 1). However, such a silicone rubber protective film and the above hard coating are different in the performance of the surface hardness required, and even when this process is applied to curing of a hard coating agent, no satisfactory abrasion resistance can be imparted to a coating film obtainable.
Therefore, it has been desired to develop a hard coating agent which is capable of imparting sufficient abrasion resistance to a transparent resin substrate made of a polycarbonate type resin or the like expected to be useful as various window materials, particularly window materials for vehicles and which is capable of maintaining its excellent properties such as the transparency and fracture resistance for a long period of time, and a process for producing a resin substrate having a hard coating layer, which is capable of forming hard coating having sufficient abrasion resistance on the resin substrate.